MTTD calculator

Compare mean, median and range while keeping missing and excluded incidents visible.

Free to use. Save a file draft or explicitly enable storage on this device.

Current result

Mean Unknown min · Median Unknown min · 0 of 1 selected incidents included

Incomplete or uncertain. Review the fields and warnings.

Review results

Start with your data or try an illustrative example.

Draft nameUsed in downloaded filenames.

Save on this device while I work

File drafts are available without browser storage. Current draft matches the last save or initial state.

This draft contains illustrative or practice data

Inputs & calculation

Measurement contractService, period boundaries, severity definition, inclusion rule and timestamp evidence.Offset for timestamps without a zoneFixed offset, not a daylight-saving rule. A pasted Z or ±HH:mm overrides it for that timestamp.

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CSV text

Analysis filters

ServiceSeverityDiscovery methodReporting period

Mean Unknown min · Median Unknown min

0 included of 1 selected; 1 missing, 0 invalid, 0 excluded.

Other period: Unknown min mean, 0 included. A difference alone does not establish improvement.

See individual durations and discovery methods

Each bar is one included incident; width is relative to the longest selected duration.

Discovery method	Included	Mean (min)	Missing
Unknown	0	Unknown	1

Incident records

All records remain editable below. Filters affect the report, not the stored draft.

Incident 1: Untitled · Current

Incident 1 fields

Incident labelImpact onsetFirst discoveryDiscovery methodServiceSeverityScope note / exclusion reasonPeriodExclude from calculation

Missing

Results

Review and export

This is incomplete or has review issues. You can save a draft; exports retain unknowns and warnings.

MTTD calculator report

MTTD calculator
User-entered draft; verify against source evidence.
Tool version 2 · https://aiopssre.com/mttd-calculator/
Name: Untitled

Offset for unzoned timestamps: UTC+00:00
Scope: [Not specified]
Filter: Current; service all; severity all; discovery all
Mean Unknown min; median Unknown min; range Unknown–Unknown min.
0 included / 1 selected; 1 missing, 0 invalid, 0 excluded.
Other period: mean Unknown min; 0 included. Compare only equivalent definitions and populations.
Unknown onset is missing, not zero. Undiscovered incidents cannot be counted by this calculator.

Incident	Onset	Discovery	Method	Service	Severity	Period	Excluded	Minutes	Scope note	Validation
						Current	false	Unknown		Missing

Mean and median answer different questions

Add the known onset-to-discovery durations and divide by the included incident count for the mean. Sort the same durations for the median. In the worked example, 5, 15 and 100 minutes produce a 40-minute mean and a 15-minute median. A further current-period incident has unknown onset and is reported as missing. This result describes known incidents; it cannot measure incidents you never discovered.

Use and review the result

Set a clear service and time window, check source data, then save the worksheet with your evidence. Downloads are editable; browser print can save a PDF. Illustrative examples are not production results.

Read the accompanying guide · Source and further reading

Calculation and worksheet review: September 29, 2026.

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